There has been known an electronic control unit, in which a heat sink and a housing are disposed so as to sandwich a substrate from both sides in order to protect the substrate from water, dust, and the like. For example, JP2010-238690A discloses an electronic control unit, in which a resin housing is attached to a heat sink by snap fitting.
For an electronic control unit including a heating element that is appropriately mounted on a substrate and generates heat when power is supplied thereto, as the unit is reduced in size, heat is more readily transferred from the heating element to a housing through a heat sink. When a housing is formed of a material having a low heatproof temperature such as resin as in JP2010-238690A, the housing may be deformed due to heat transferred from the heating element, leading to a reduction in attachment strength of the housing.